Add a simple XDMCP server implementation

Allows only MIT-MAGIC-COOKIE-1 authorization.

Only replies to Query type requests (no broadcast).

Doesn't support authentication.

Adds a constructor to Display class with the X server hostname
which is then propagated to the m_display variable.

Implementation of server behavior on receiving various packet types
is implemented in the virtual onServerReceived method of the Packet
class. The same will apply for client when written.

Many things aren't finished (timeouts, possible leaks and such), to
be fixed over time.